Apache reverse proxy not preserving headers@crawf if the content was modified in the 11 hours between +1100 and GMT, then yes one of those would have a stale cache. The same day an hour in +1100 and +0000 are not the same time. What are the response headers from api.domain.com the first time (before the client has the resource in its cache)? I do notice the If-Modified-Since and Last-Modified headers have the same time. Maybe that is significant?